Abstract
Banding of N fertilizers below the seed is a common practice in direct seeded wheat dominated dryland agricultural systems, yet the placement of fertilizer below the seed has been shown to decrease yields and damage the root system architecture (RSA) in canola ( Brassica napus ). However, there is a lack of understanding as to which rates and sources of fertilizers might be safe for seedling root systems. The goal of this study was to compare the effect of three different N sources over a gradient of application rates on canola RSA. The effect of the fertilizer band on RSA has previously been imaged using rhizobox methods. However, the research presented here describes a novel technique for comparing sources and rates simultaneously while using the existing imaging technology. Canola seedlings were exposed to increasing rates of urea, ammonium sulfate (AS), and urea ammonium nitrate (UAN) from 0 mg N cm –1 to 40 mg N cm –1 placed 50 mm below the seed row. Canola showed significant changes in RSA as a result of the increasing ammoniacal‐N fertilizer rate. Dose response curves were developed for urea, AS, and UAN, and median lethal doses (LD50s) for tap roots were estimated at 4.7, 9.7, and 20.6 mg N cm –1 , respectively. Comparisons between multiple measurements of the dose response curves revealed a consistent ranking of relative potencies among urea, AS, UAN (most to least toxic). Core Ideas New assay method for determining the relative potencies and safety ranges of different fertilizer sources as relates to roots system damage. Banded urea, ammonium sulfate, and urea ammonium nitrate N fertilizer sources all damage canola seedling root systems, but at differing rates. Dose response analysis was utilized to rank the relative potencies of ammoniacal‐N fertilizers from most toxic (urea) to least toxic (urea ammonium nitrate).
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Claims 5
Claim · model-written summary
Increasing ammoniacal nitrogen fertilizer rates significantly changed canola root system architecture.
- Taxon
- Canola
.jpg?width=60)
Brassica napus var. napuse0 - Treatment
- increasing ammoniacal‐N fertilizer ratee0
- Outcome
- RSAe0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Canola showed significant changes in RSA as a result of the increasing ammoniacal‐N fertilizer rate.”
Claim · model-written summary
Urea tap-root LD50 was estimated at 4.7 mg N per cm.
- Taxon
- CanolaBrassica napus var. napuse1
- Treatment
- ureae0
- Outcome
- median lethal doses (LD50s) for tap rootse0
- Value
- 4.7e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dose response curves were developed for urea, AS, and UAN, and median lethal doses (LD50s) for tap roots were estimated at 4.7, 9.7, and 20.6 mg N cm –1 , respectively.”
e1“Canola seedlings were exposed”
Claim · model-written summary
Ammonium sulfate tap-root LD50 was estimated at 9.7 mg N per cm.
- Taxon
- CanolaBrassica napus var. napuse1
- Treatment
- ASe0
- Outcome
- median lethal doses (LD50s) for tap rootse0
- Value
- 9.7e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dose response curves were developed for urea, AS, and UAN, and median lethal doses (LD50s) for tap roots were estimated at 4.7, 9.7, and 20.6 mg N cm –1 , respectively.”
e1“Canola seedlings were exposed”
Claim · model-written summary
Urea ammonium nitrate tap-root LD50 was estimated at 20.6 mg N per cm.
- Taxon
- CanolaBrassica napus var. napuse1
- Treatment
- UANe0
- Outcome
- median lethal doses (LD50s) for tap rootse0
- Value
- 20.6 mg N cm –1e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dose response curves were developed for urea, AS, and UAN, and median lethal doses (LD50s) for tap roots were estimated at 4.7, 9.7, and 20.6 mg N cm –1 , respectively.”
e1“Canola seedlings were exposed”
Claim · model-written summary
Dose-response measurements consistently ranked urea most toxic, then AS, then UAN.
- Taxon
- CanolaBrassica napus var. napuse1
- Outcome
- consistent ranking of relative potenciese0
- Qualifier
- most to least toxice0
- Comparator
- urea, AS, UANe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Comparisons between multiple measurements of the dose response curves revealed a consistent ranking of relative potencies among urea, AS, UAN (most to least toxic).”
e1“Canola seedlings were exposed”
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